Stress waves in layered cellular materials—Dynamic compaction under axial impact

• Theoretical models are developed to describe the propagation of stress waves in layered foam.
• The simultaneous propagation of waves of strong discontinuity and simple waves is discussed.
• Multiple reflections of the waves of strong discontinuity from the layer interfaces are analysed.
• The maximum stresses within the specific layers depending on the density sequence are studied.
• A comparison between the dynamic responses of layered and uniform density blocks is reported.

Theoretical analysis of the propagation of stress waves in layered cellular solids with different densities, and consequently strengths, is carried out to deepen the understanding of their dynamic compaction due to impact loading. The cellular topology is neglected and homogeneous properties are assumed. Two types of plastic waves are distinguished depending on the layers density arrangement. Only waves of strong discontinuity occur when the layers’ densities increase in the direction of propagation of the primary wave. Multiple reflections of the stress waves from the layer interfaces are identified and studied for this type of the layers density arrangement. Simultaneous propagation of a wave of strong discontinuity in the proximal layer and a simple wave in the subsequent layers occur when the layers’ densities decrease in the direction of propagation of the primary wave.Two types of loading conditions: an impact of a stationary cellular block by a rigid mass and an impact of a cellular block on a rigid wall are analysed. It is assumed that the constituent materials in the layered solids exhibit strain hardening. The plastic strain is sought as a function of the impact velocity and material properties when using the characteristic Hugoniot strain–velocity relationship. FE models using ABAQUS are constructed and numerical simulations are carried out to verify the predictions of the theoretical analysis. The potential of layered cellular materials to design more efficient structural components when subjected to intensive dynamic loading is briefly discussed when comparing the response of some layered configurations with their uniform density counterparts of equal mass.